1. Field of the Invention
The present invention relates to a surface-coated polymer actuator and a method of preparing the same, and more particularly, to a surface-coated polymer actuator which can prevent the leakage of a solvent from an electrode's surface, and a method of preparing the same.
The present invention has been deduced from a research performed as a part of the Component Modules for Ubiquitous Terminal Business Planning by the Ministry of Information and Communication (South Korea) [2006-S-006-02, Component Modules for Ubiquitous Terminal].
2. Discussion of Related Art
Lately, many scientists have been actively conducting research on ionic polymer metal composites (IPMCs), which is one of electroactive polymers (EAPs) [Sia Nemat-Nasser and Chris W. Thomas, Electroactive polymer (EAP) actuators as artificial muscles: reality, potential and challenges, SPIE press, Washington, 2001].
Particularly, among various kinds of EAPs, the IPMC has advantages of low power consumption, large displacement at low voltage, and a fast response time in high frequency [M. Shahinpoor, Y. Bar-Cohen, J. O. Simpson, J. Smith, Smart Materials and Structures, 1998, 7, R15].
The IPMC consists of a fluorinated ionic polymer membrane such as a Nafion™ membrane, and a conductive metal, wherein both surfaces of Nafion™ are electroplated with metal electrodes. As seen in FIG. 1, when cations in the membrane are moved by applying an electrical field to the metal electrodes, the membrane is swollen, and bent in the opposite direction to the movement of the cations, which results in the transformation of the membrane in the electrical field. Such transformation can be adjusted according to cations which are electrolytes present in the IPMC, a solvent (e.g., water, polar solvent or ionic liquid) delivering the cations, a voltage applied to the electrodes disposed on both the surfaces of the membrane, or a frequency [Barbar J. Akle and Donald J. Leo, SPIE, 2003, 5051, 214].
Most actuators use water as a polar solvent, preparation of which is simple. However, such an actuator is limited in use at very high and low temperatures due to boiling and melting points of water. For example, due to water's freezing and boiling points, the actuator is difficult to be operated under 0° C., and less stable at high temperature required in a module manufacture. To solve these problems, scientists employ ionic liquids taking advantage of melting and boiling points [M. D. Bennett, D. J. Leo, G. L. Wilkes, F. L. Beyer, T. W. Pechar Polymer, 2006, 47, 6782; Doyeon Kim and Kwang J. Kim, SPIE, 2006, 6168, 616811].
To enhance the stability of a polymer actuator, a search for improving contact between a Nafion™ membrane and a metal electrode to overcome performance degradation of the actuator caused by the detachment of the metal electrode which may occur during the actuation of the polymer actuator is actively progressing. As a part, a sandblasting or plasma treatment method has been developed and disclosed [S. J. Lue, T. S. Shin, T. C. Wei, Korean J. Chem. Eng. 2006, 23, 441]. However, this method cannot prevent the leakage of a solvent caused by damage of a metal electrode itself, and thus cannot overcome decreasing drivability and stability of the polymer actuator.
Accordingly, the present inventors found that a polymer actuator which can overcome the leakage of a solvent or an electrolyte and improve displacement and drivability is prepared by coating surfaces of an electrode of a polymer actuator with a compound having elasticity and chemical durability, and the present invention was completed.